Microstrip ferrite phase shifters having time segments varying in length in accordance with preselected phase shift characteristic

ABSTRACT

An electronically controllable RF (radio frequency) phase shifter that can be designed to provide either true time delay characteristics or constant phase versus frequency characteristics. The non-reciprocal microstrip phase shifters of the invention utilize a ferrimagnetic substrate with a metallized strip conductor on one face and a metallized ground plane on the other face. The strip conductor has a plurality of adjacent line sections selected to provide a circularly polarized RF magnetic field at a point between each two adjacent conductors with the plane of the circularly polarized magnetic field being orthogonal to the plane of a DC magnetic bias field, the latter plane being provided parallel to the face of the substrate. The circularly polarized RF magnetic field is developed by selecting the line sections with a length so that the signals in adjacent lines are 90* out of phase from each other. When either the level or direction of the DC bias is changed, the permeability of the ferrimagnetic material changes causing a change in the propagation constant and a resultant phase shift change. To provide a relatively wide bandwidth to the phase shifter and a desired delay characteristic, the adjacent conductor sections have their line length varied so that different portions of the line effects the phase shift for different frequencies.

United States Patent [191 Charlton et al.

[ Aug. 14, 1973 MICROSTRIP FERRITE PHASE SHIFTERS HAVING TIME SEGMENTSVARYING IN LENGTH IN ACCORDANCE WITH PRESELECTED PHASE SHIFICHARACTERISTIC [76] Inventors: Donald A. Charlton, 21 131 Miramar Ln.,Huntington Beach, Calif. 92646; William P. Clark, 3934 Greenwood Ave.,Orange, Calif. 92667 [22] Filed: Sept. 27, 1971 [21] Appl. No.: 184,136

[ ABSTRACT An electronically controllable RF (radio frequency) phaseshifter that can be designed to provide either true time delaycharacteristics or constant phase versus frequency characteristics. Thenon-reciprocal microstrip phase shifters of the invention utilize aferrimagnetic substrate with a metallized strip conductor on one faceand a metallized ground plane on the other face. The strip conductor hasa plurality of adjacent line sections selected to provide a circularlypolarized RF magnetic field at a point between each two adjacentconductors with the plane of the circularly polarized magnetic fieldbeing orthogonal to the plane of a DC magnetic bias field, the latterplane being provided parallel to the face of the substrate. Thecircularly polarized RF magnetic field is developed by selecting theline sections with a length so that the signals in adjacent lines are 90out of phase from each other. When either the level or direction of theDC bias is changed, the permeability of the ferrimagnetic materialchanges causing a change in the propagation constant and a resultantphase shift change. To provide a relatively wide bandwidth to the phaseshifter and a desired delay characteristic, the adjacent conductorsections have their line length varied so that different portions of theline effectsthe phase shift for different frequencies.

3 Claims, 8 Drawing Figures Source |0q Periodic.

linear Disiribuiion Disi r'lbui'io I Ferrimaqneiic H I Subsi'ral'g l l j90 L -Cons+an+ Phase Charaici'er-is'iic HAVING TIME SEGMENTS VARYING INLENGTH IN ACCORDANCE WITH PRESELECTEI) PHASE SHIFT CHARACTERISTICBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to RF phase shifters and particularly to an electronicallycontrolled RF phase shifter having a wide bandwidth and having desiredphase shift characteristics such as true time delay or constant phaseversus frequency.

2. Description of the Prior Art Two basic families of wide bandwidth RFphase shifter devices would be desirable for different applications,with the first family having the characteristic of true time delay andthe second family having the characteristic of constant phase versusfrequency. The true time delay phase shifters could be employed inantenna array applications, and the constant phase versus frequencyphase shifters could be employed as the active phasing device in Butlermatrix applications, in Blass matrices and in switchable four-portdifferential phase shift circulators. Suitable phase shifters with truetime delay characteristics are presently not known, and prior art phaseshifters with a constant phase versus frequency characteristic havebandwidth limitations. In the past, systems and devices have beenlimited to the bandwidth of the phase shifters, approximately 12percent, thus providing a substantial limitation to the systemoperation. Another substantial requirement for phase shifters in certainoperations is that the amount of phase shift be electronicallycontrollable.

SUMMARY OF THE INVENTION Briefly, the phase shifters in accordance withthe invention are non-reciprocal, microstrip ferrite phase shiftersfabricated by using a ferrimagnetic substrate with a metallizedconductor line on one face or surface, positioned to form a plurality ofadjacent line segments and with a metallized ground plane on the otherface.

The devices develop a circularly polarized RF magnetic field betweenadjacent line segments in a plane orthogonal to the plane of a DCmagnetic bias field, the latter plane being perpendicular to the planeof the substrate. The circularly polarized RF magnetic field isgenerated by selecting the length of the line segments to provide the RFsignal 90 out of phase in the adjacent line segments. In response to aDC magnetic bias applied to the substrate, either the level or directionof the DC magnetic field or magnetic bais field is changed so that thepermeability of the substrate material is controlled with a resultantdesired phase shift-Due to the closed magnetic path in the substrate,the DC magnetic field remains constant without a continuously appliedexternal driving source. Any desired number of phase shift conditionsmay be selected by controlling the DC magnetic bias. In order to providea phase shift versus frequency characteristic that is either true timedelay or constant phase, the length of the line segments are varied withIt is therefore an object of this invention to provide an improvedmicrostrip RF phase shifter having desired time delay characteristics.

It is another object of this invention to provide an improved RF phaseshifter device having a substantially wide bandwidth.

It is another object of this invention to provide an improvedelectronically controllable phase shifter for reliably selecting desiredphase shift characteristics.

It is another object of this invention to provide RF phase shifters thatcan be developed to provide a characteristic of true time delay or toprovide a characteristic of constant phase versus frequency.

It is still another object of this invention 0 provide an electronicallycontrolled microstrip RF phase shifter that has a wide bandwidth andthat has a desired time delay characteristic.

BRIEF DESCRIPTION OF THE DRAWINGS skilled in the art in the light of thefollowing detailed description taken in consideration with theaccompanying drawings wherein like reference numerals indicate like orcorresponding parts throughout the several parts:

FIG. 1 is a schematic diagram of a simplified microstrip phase shifterutilizing a meander line for explaining the operation thereof inaccordance with the principlesof the invention;

FIG. 2 is a schematic sectional drawing taken at line 2-2 of FIG. 1 forexplaining the theory of operation thereof;

FIG. 3 is a schematic diagram of vectors useful in explaining theoperation of the phase shifters by' reference to FIG. 2;

FIG. 4 is a schematic diagram of a microstrip phase shifter utilizing ameander line with alog-periodic line length distribution and indicatingother possible line length distributions in accordance with theinvention;

FIG. 5 is a schematic diagram of hysteresis curve of magnetic fluxdensity versus current for explaining the DC magnetic bias utilized toprovide the electronically controlled phase shifts in accordance withthe invention;

FIG. 6 is a schematic plan view of a single conductor microstrip phaseshifter in a circular orspiral format in accordance with the invention;

FIG. 7 is a schematic diagram of phase shift versus frequency forexplaining the characteristics and these lection of characteristics ofthe phase shifters in accordance with the invention; and

FIG. 8 is a curve of phase shift versus frequency showing experimentalresults from "the performance of a phase shifter in accordance with FIG.4 having a logperiodic line length variation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2,a simplified ferrimagnetic phase shifter 10 in accordance with theinvention may be fabricated by using a ferrimagnetic substrate 12 whichmay be of any suitable material such as ferrite or garnet with ametallized strip conductor 14 on oneface and a metallized ground plane18 on the other face. The conductors utilized in the phase shifters ofthe invention may be of any suitable conductive material such asaluminum, copper, silver, gold, for example, and may be deposited ormounted on the substrate by any suitable technique. For example, theconductor may be a thin film deposited by vapor-deposition or bysputtering, or may be a film placed on the substrate by a thick filmprocess in which a mixture including silver and glass particles arepainted on the substrate and then fused in an oven. A source of RF inputsignals 20 applies RF (radio frequency) signals to the line 14 to exciteline segments 15, 16 and 17. Each line segment such as 16 has a linelength or line segment length between points such as 23 and 25 orbetween similar points. Coupled to the lead 14 at the output of thephase shifter is a utilization unit 28. For electronically controllingthe DC (direct current) magnetic field in the substrate 12, a pulsecontrol source 30 is provided for appplying current pulses of a waveform31 through a lead 32 which is wound through an opening or hole 36 in thesubstrate, to establish the DC magnetic field or magnetic state thereinindicated by a dashed line 33. The pulse control source 30 is a suitablevoltage driving source controlled to selectively provide current pulsesof the waveform 31 with a predetermined amplitude and of a predeterminedduration. The control source 30 in some arrangements in accordance withthe invention for a digital source, may include a current source, aswitch such as a single pole double throw switch selectively passingpositive or negative current pulses from the source through a gate tothe drive line 32, with a peak current sensor controlling the gate inresponse to the drive line current reaching a predetermined level, as iswell known in the art. The control source 30 for some arrangements inaccordance with the invention for an analog source, may include avoltage source, switch such as a single pole double throw switchselectively passing either positive or negative current pulses to a gateand a controllable counter closing the gate for selected periods of timeto pass pulses to the drive line 32. It is to be understood that thecontrol source 30 is not limited to any particular arrangement but mayinclude any suitable mechanization in accordance with the invention.

A first requirement for the non-reciprocal phase shifter in accordancewith the invention is that the RF magnetic field be circularly polarizedat a point A in the material. The line length of line segments such asand 16 is equal to a quarter wavelength of the RF signal frequency sothat adjacent signals are 90 out of phase from each other to develop thecircularly polarized region. The line length for the effected signal is)./4 or n). )./4 where 1; is any integer and X is the wavelength of theRF signal effected or phase shifted at that line area. The secondrequirement for the phase shifter of the invention is that a DC magneticfield be produced orthogonal to the plane of the circularly polarizedfield developed at point A and a third requirement is that the RF signalmust pass through that RF circular polarized region A. The DC magneticfield H is shown passing into the paper in the region of the linesegments in FIG. 2 by arrowheads 48 and 50 and coming out of the paperin a region away from the meander line by an arrow point 47, asdeveloped by the conductor 32.

Referring now also to FIG. 3, the RF signal passing through linesegments 15 and 16 shown as 1,, for each line segment at a time t O arerespectively maximum in the line segment 15 with current conducting intothe plane of the drawing and has a value of zero in the line segment 16.The magnetic field h at point A has the direction and magnitude of avector 36 resulting from magnetic fields 34 and 35 (when current flowsthrough the conductors). At a second time t T/4 where T is the period ofa cycle of the RF signal, the RF current is at a zero level through theline segment 15 and is passing with a maximum amplitude through the linesegment 16 in a direction into the paper. As a result, the magneticfield has a valve and amplitude of a vector 38. At a time t T/2, RFcurrent passes through the line segment 15 with a maximum amplitude in adirection out of the paper and zero current passes through the linesegment 16 to provide a magnetic vector 40 at point A. At a fourth timet 3T/4 zero current passes through the line segment 15 and current ofmaximum amplitude passes through the line segment 16 in a direction outof the paper, resulting in a magnetic vector 41 at point A. Thus, acircular polarized condition is developed at the point A and anelliptically polarized condition is developed in adjacent regions suchas 44 and 46. It is to be noted that the interaction which provides thephase shift in accordance with the invention is developed in theelliptically polarized regions as well as at the circularly polarizedregion or point A. Less interaction is provided in the ellipticalpolarized regions than in the circularly polarized regions. It is to benoted that a similar circularly polarized point A is developed betweeneach pair of conductors for acting on the RF phase such as betweenconductors l6 and 17 as well as between conductors 15 and 16.

The operation of the DC magnetic bias field H orthogonal to the plane ofthe circular polarization will now be further explained. The ferritematerial 12 may be considered as being divided into magnetic domains,each domain having its atoms with a certain moment and a certaindirection and angle of precession. The electrons spin in each domainwith a certain moment as determined by that group of atoms. When a DCmagnetic field is provided, all of the domains align so that the atomshave the same direction of moment and the same precession angle. The RFmagnetic field changes the precession angle of the atom due to theinteraction of the magnetic forces. A change of the precession angles ofthe atoms changes the effective permeability of the ferrite material andin turn the amount of time delay provided therethrough, resulting in adifferent phase shift. For example, an increase of the precession anglesof the spinning atom, increases the effective permeability of theferrite, slows down the transfer of the RF signal therethrough andprovides a larger phase shift. The DC field which is orthogonal to theplane of the RF field controls the direction of the magnetic moment andtherefore the direction of the precessional spin relative to thedirection of the circularly polarized magnetic field, thus changing theeffective permeability of the ferrite. For example, if the DC fieldchanges to its opposite direction of polarity, the precession is in theopposite direction and the precession angle will be smaller whichresults in a reduction of the RF energy density. Since the groupvelocity of RF energy passing through the ferrite type material is equalto the power flow density divided by the energy density in the ferrite,a reduction of energy density will cause an increase in group velocity.Thus, the phase shifter of the invention provides an effective change inthe material so that the energy passes through the ferrite at selectedspeeds, the

change in material being a change in the RF permeability of theferrimagnetic material.

Referring now to FIG. 4 which shows a phase shifter 60 having a singleconductor 64 as a meander lineand which is formed of a ferrimagneticsubstrate 68' on which the conductor 64 is deposited orpositioned toestablish the meander line generally indicated as 70. A ground plane(not shown) is provided as shown in FIG. 2. In the illustratedarrangement, the line length defined as the distance between points 72and 74, for example, is varied along the meander line in accordance withselected characteristics such as log-periodically so that the longerlines on the left-hand side of the device provides a phase shift at thelower operating frequencies and the shorter lines at the right-handsideof the device provides a phase shift at the higher operatingfrequencies. The meander line 70 is shown with a log periodicdistribution of line length to provide a true time delay phase shiftcharacteristic. Other variations are linear having a configuration ofdotted lines 78 and 79 and a variation of lines 80 and 81 which may beselected to provide a constant phase characteristic. The variation ofthe line length is such that a phase shift only occurs in the group oflines whose length is approximately equal to a quarter wavelength of theoperating frequency because this is the only frequency at which acircular polarized condition is developed at the point A and othersimilar points as explained relative to FIG. 2. For the log-periodicline length distribution, every frequency is effected by an equal numberof lines, but not bythe same ones, and a wide bandwidth operation isachieved as well as the desiredphase shift versus frequencycharacteristic. For line length distributions other than log-periodicfor providing other desired phase shift versus frequencycharacteristics, different frequencies are effected by different numbersof lines but a substantially wide bandwidth is achieved.

When the line length is varied log-periodically, as shown in FIG. 4, forexample, and the line spacing such as 75 is held constant, a true timedealy characteristic is achieved. A log-periodic distribution means thatfor adjacent line segments equally spaced along the meander line, eachadjacent line segment length varies as a constant, K, times the lengthof the previous adjacent line segment. The DC magnetic field is providedby passing conductor 86 through openings 88 and 90 in the substrate 68so that the DC magnetic fields are all in the same direction, andapplying a DC control current therethrough from a DC control source 94.The line 64 has an input port 98 and an output port 100 thus requiringonly a single strip conductor being placed upon the substrate 68.

When the line segments of the meander line of FIGS. 2 and 4 have alength 1;) M4 and 1; is an integer greater than zero, some additionalloss may be developed. In this condition with additional wavelengths,there are additional circular polarized points along the center betweenadjacent conductor segments. The RF rotation changes direction betweenadjacent circular polarized points by a change from a circularpolarization point to elliptical and then to linear and then back toelliptical and a circular polarized point. For a line length of A +IA/4there are five points (like point A) between adjacent segments withthree providing a positive phase shift and two providing a negativephase shift to develop a net positive phase shift, for example. For aline length of 2A H4 there are nine points with five providing apositive phase shift and four providing a net positive phase shift, forexample.

Referring now also to FIG 5 which shows the hysteresis curve of theferrimagnetic material 68, the control source 94 may provide digitalcontrol so that the material is in either state 103 or 105 resulting ina reversal of the polarity of the magnetic moment. Also within the scopeof the invention, the control source 94 may select any analogmagneticstate such as 107 to 110 for respective phase shifts of 45, 90, 180 or270, for example. TheDC source 94 may be a suitable circuit for digitalor analog operation as discussed relative to FIG. 1. For analogoperation the source: 94 may be any suitable voltage source circuit aswell known in the art for providinga predetermined voltage for apredetermined time for each controlled phase shift state.

Referring now to FIG. 6 which shows a single conductormicrostrip phaseshifter employing a circular'or spiral format and which, for example,may have a log-periodic variation of circular line segment length of aplurality of adjacent line segments. The spiral phase shifter includes aferrimagnetic substrate 122 and a spirally arranged strip conductor 124having a first port 126 and a second port 128 either of which may be theinput or output ports. A ground plane (not shown)is provided as shown inFIG. 2. The spiral is arranged so that the distance around any circularportion or'line segment of the conductor such as portions 130 and 132from a position of a line 134is 90 less for the signal in the innerportion 132 than in the outer portion 130. The line segments are spacedfrom each other as a function of the selected line length distribution.The length of each portion further out from the next inner portion is M4more than the adjacent inner segment. The k spiral segment has a length1 A,, )t /4 where 1; is 0 or any integerand )t is the wavelength whichreceives a maximum phase shift in this segment. Thus, for each linesegment, 1 a different frequency as defined by the expression r k+ )t/41,, receives the maximum phase shift. The length of adjacent segmentsisvaried as a selected function (such as log-periodic) so that the 90phase difference is provided between adjacent segments and so thatfrequencies are effected in each line as defined by the A of that line.Each of the circular line segments may control only the RF signal at asingle frequency (as defined by the A used in the line length) or narrowband of frequencies in the phase shifter bandwidth. In the spiralconfiguration a continuous line of the point A circularly polarizedcondition is provided between the conductors. A DC conductor 136 passesthrough the opening 141 to provide. a DC magnetic field of dotted lines137 and maybe controlledby a suitable digital or analog pulse controlsource such as source 30 of FIG. 1 or source 94 of FIG. 4.

Referring now also to FIG. 7, the selection of the line lected toprovide a constant phase shift versus fre-.

quency characteristic, a wide frequency band ofppe'i'ation is providedas shown by a curve 71. One arrangement'for determining the line lengthdistribution of the conductor segments is to draw from calculated orexperimental phase shift amplitudes, curves such as 70, 72 and 74, eachfor a portion of the conductor segmcnts bctwecn the input and outputterminals. Longer line length at the input provides a phase shift atlower frequencies as shown by the curve 70 and the shorter line lengthsat the output provides a phase shift at higher frequencies as shown by acurve 74. The curve 72 may represent the phase shift at the centralportion along the length of the conductor. Any number of curves may beutilized to provide this graphical distribution of line lengths. Thecombined result, when the line length distribution is properly selectedto provide proper curves such as 70, 72 and 74, is the resultant phaseshift curve 69, for example, when the line length between the twoadjacent conductor segments is logperiodic, that is, the line length foreach segment is a constant times the line length of the previous segment(for equal line spacing). Thus, any desired phase shift versus frequencycurve such as 69 or 71 may be provided in accordance with the invention.It has been determined in accordance with the invention, that for a truetime delay the variation in line length is typically log-periodic. For alog-periodic variation, the amount of line segments utilized for thedifferent frequencies is less for the lower frequencies andsubstantially more for the higher frequencies. For a constant phaseshift versus frequency characteristic the distribution of the linelengths is more line segments for the low frequencies and less linesegments for the high frequencies. The distribution may be determined,for example, either by computer simulation, by graphical simulation asexplained relative to FIG. 7, or by calculation or experimentally.

Referring now to FIG. 8 which shows an experimental curve 170 of phaseshift versus frequency developed from the phase shifter of FIG. 4 havinga log-periodic line distribution. The constructed phase shifter providedapproximately one wavelength or 360 or true time delay phase shift overthe frequency band of 5.0 to 6.0 GHz (gigahertz). The length of thelines were varied log-periodically and the spacing was held constant toprovide a true time delay. The device performance was in accordance withthe solid curve 170 and the frequency band of operation represents abandwidth of 18 percent. It is to be noted that this achieved bandwidthis not an inherent limitation to the device but rather resulted from aparticular design. Broken lines 17] and 173 show a theoretical perfecttrue time delay characteristic. The solid experimental line 170 varies arelatively small amount from the theoretically perfect characteristic.In addition to this wide bandwidth performance, the device could beswitched from one phase state to a second within five microseconds. Theenergy required to perform the switching operation was 20 microjoules.The size of the constructed device was 1.0 X 2.0 X 0.025 inches with aweight of 4.6 grams (0.010 lbs.).

Thus there has been provided electronically controllable RF phaseshifters which may develop over a 360 phase shift. a characteristic oftrue time delay or which may be designed to provide a constant phaseversus frequency characteristic. The phase shifters in accordance withthe invention provide a bandwidth substantially greater than any similartype devices known in the art today. The phase shifters of the inventionoperate with either terminal or port being the input so that the inputRF signal can be applied initially to either the short or the long linesegments. The principles of the invention include controlling the phaseshift electronically and varying the line length length in theconfiguration of a meander line or other arrangements having adjacentline segments. The phase shifter devices which employ log-periodic linespacing develop a true time delay in accordance with the principles ofthe invention. However, it is to be understood that phase shiftershaving a line spacing other than log-periodic such as to develop aconstant phase versus frequency characteristic are within the scope ofthe invention.

What is claimed is:

l. A wide bandwidth RF phase shifter responsive to applied controlsignals, for phase shifting applied RF signals and wherein the relativephase shift across the bandwidth is in accordance with a preselectedfunction of the frequency of the RF signals, said device comprismg:

a ferrimagnetic substrate having first and second surfaces;

a ground plane conductor on the first surface of said substrate;

a continuous conductor on the second surface of said substrate saidconductor being a meander line having a plurality of equally spacedsubstantially parallel adjacent line segments with the length of theadjacent line segments varying log-periodically from one end to theother end of said meander line; whereby the phase delay applied to saidRF signals is approximately a linear function of the frequency of saidRF signals.

means for applying said Rf input signals to a first end of saidconductor;

output means for receiving the RF signals from a second end of saidconductor; and

means for providing a DC magnetic bias field in said substrate inresponse to the applied control signals;

whereby the value of phase delay applied to said RF signals iscontrollable in response to said control signals, and the relative phaseshift across the bandwidth is in accordance with a predeterminedfunction of frequency established by said preselected segment lengthdistribution pattern.

2. A wide bandwidth RF phase shifter responsive to applied controlsignals, for phase shifting applied RF signals and wherein the relativephase shift across the bandwidth is in accordance with a preselectedfunction of the frequency of the RF signals, said device comprismg:

a ferrimag netic substrate having first and second surfaces;

a ground plane conductor on the first surface of said substrate;

a continuous conductor on the second surface of said substrate saidconductor being a meander line having a plurality of equally spacedsubstantially parallel adjacent line segments with the length of theadjacent line segments varying approximately linearly from one end tothe other end of said meander line,

means for applying said RF input signals to a first end of saidconductor;

output means for receiving the RF signals from a second end of saidconductor; and

means for providing a DC magnetic bias field in said substrate inresponse to the applied control signals;

whereby the value of phase delay applied to said RF signals iscontrollable in response to said control signals, and the relative phaseshift across the bandwidth is in accordance with a predeterminedfunction of frequency established by said preselected segment lengthdistribution pattern.

3. A wide bandwidth RF phase shifter responsive to applied controlsignals, for phase shifting applied RF signals and wherein the relativephase shift across the bandwidth is in accordance with a preselectedfunction of the frequency of the RF signals, said device comprismg:

a ferrimagnetic substrate having first and second surfaces;

a ground plane conductor on the first surface of said substrate;

a continuous conductor on the second surface of said substrate saidconductor having a generally spiralshaped configuration from one end tothe other end thereof with each turn of said spiral forming a conductorsection and with adjacent conductor sections varying in length from afirst end to a second end of said spiral in accordance with alogperiodic distribution pattern; whereby the phase delay applied tosaid RF signals is approximately a linear function of the frequency ofsaid signals;

means for applying said RF input signals to a first end of saidconductor;

output means for receiving the RF signals from a second end of saidconductor; and

means for providing a DC magnetic bias field in said substrate inresponse to the applied control signals;

whereby the value of phase delay applied to said RF signals iscontrollable in response to said control signals, and the relative phaseshift across the bandwidth is in accordance with a predeterminedfunction of frequency established by said preselected segment lengthdistribution pattern.

1. A wide bandwidth RF phase shifter responsive to applied controlsignals, for phase shifting applied RF signals and wherein the relativephase shift across the bandwidth is in accordance with a preselectedfunction of the frequency of the RF signals, said device comprising: aferrimagnetic substrate having first and second surfaces; a ground planeConductor on the first surface of said substrate; a continuous conductoron the second surface of said substrate said conductor being a meanderline having a plurality of equally spaced substantially paralleladjacent line segments with the length of the adjacent line segmentsvarying logperiodically from one end to the other end of said meanderline; whereby the phase delay applied to said RF signals isapproximately a linear function of the frequency of said RF signals.means for applying said Rf input signals to a first end of saidconductor; output means for receiving the RF signals from a second endof said conductor; and means for providing a DC magnetic bias field insaid substrate in response to the applied control signals; whereby thevalue of phase delay applied to said RF signals is controllable inresponse to said control signals, and the relative phase shift acrossthe bandwidth is in accordance with a predetermined function offrequency established by said preselected segment length distributionpattern.
 2. A wide bandwidth RF phase shifter responsive to appliedcontrol signals, for phase shifting applied RF signals and wherein therelative phase shift across the bandwidth is in accordance with apreselected function of the frequency of the RF signals, said devicecomprising: a ferrimagnetic substrate having first and second surfaces;a ground plane conductor on the first surface of said substrate; acontinuous conductor on the second surface of said substrate saidconductor being a meander line having a plurality of equally spacedsubstantially parallel adjacent line segments with the length of theadjacent line segments varying approximately linearly from one end tothe other end of said meander line, means for applying said RF inputsignals to a first end of said conductor; output means for receiving theRF signals from a second end of said conductor; and means for providinga DC magnetic bias field in said substrate in response to the appliedcontrol signals; whereby the value of phase delay applied to said RFsignals is controllable in response to said control signals, and therelative phase shift across the bandwidth is in accordance with apredetermined function of frequency established by said preselectedsegment length distribution pattern.
 3. A wide bandwidth RF phaseshifter responsive to applied control signals, for phase shiftingapplied RF signals and wherein the relative phase shift across thebandwidth is in accordance with a preselected function of the frequencyof the RF signals, said device comprising: a ferrimagnetic substratehaving first and second surfaces; a ground plane conductor on the firstsurface of said substrate; a continuous conductor on the second surfaceof said substrate said conductor having a generally spiral-shapedconfiguration from one end to the other end thereof with each turn ofsaid spiral forming a conductor section and with adjacent conductorsections varying in length from a first end to a second end of saidspiral in accordance with a log-periodic distribution pattern; wherebythe phase delay applied to said RF signals is approximately a linearfunction of the frequency of said signals; means for applying said RFinput signals to a first end of said conductor; output means forreceiving the RF signals from a second end of said conductor; and meansfor providing a DC magnetic bias field in said substrate in response tothe applied control signals; whereby the value of phase delay applied tosaid RF signals is controllable in response to said control signals, andthe relative phase shift across the bandwidth is in accordance with apredetermined function of frequency established by said preselectedsegment length distribution pattern.